Metalcraft Of Mayville, Inc. v. The Toro Company, 848 F.3d 1358, 1367 (Fed. Cir. 2017) ("Without any explanation as to ... why the references would be combined to arrive at the claimed invention, we are left with only hindsight bias that KSR warns against ... we cannot allow hindsight bias to be the thread that stitches together prior art patches into something that is the claimed invention.").